Select Page

Residential High Performance Attics / Ducts in Conditioned Spaces (HPA/DCS)

Building Envelope

Measure Overview

The Residential High Performance Attics (HPA) and Ducts in Conditioned Space (DCS) are the proposed options for the prescriptive envelope package. Both of these measures improve building thermal envelope and reduced HVAC distribution losses in residential buildings. These two approaches will have similar energy impacts on the building.

  • High Performance Attics (HPA) implements measures that minimize temperature difference between the attic space and the conditioned air being transported through ductwork in the attic. The package consists of R-13 insulation below the roof deck or R-6 insulation above the roof deck, R-38 insulation at the ceiling, R-8 ducts, and 5% total duct leakage of the nominal air handler airflow.
  • Ducts in Conditioned Space (DCS), locates ducts and air handlers in the building’s thermal and air barrier envelope. This measure requires field verification in order to meet the prescriptive requirement. Installing ductless systems meets the DCS requirement.

The proposed measure will add or modify prescriptive requirements related to attic, roof, air handler, and ducts in residential buildings. The proposed measures will modify compliance options for ductless systems and add or modify modeling procedures for all of the above measures in the performance method.

As a result of the change, the Standards will address energy issues related to air losses from air handlers and ducts in attics while allowing compliance options to meet the requirements with alternate systems or strategies. The proposed change does not modify or expand the scope of the Standards themselves.

Stakeholder Meeting

Several stakeholder meetings and CEC staff workshops were held regarding the HPA/DCS building energy efficiency topic. The list of past meetings and hearings can be found here. If you would like to receive email updates on this CASE topic, click the link below


  1. Final CASE Report